The present invention relates to an ink ejectability maintenance device for maintaining constant ink ejectability of a recording head for ejecting ink droplets toward a recording medium, as well as to a recording apparatus equipped with the ink ejectability maintenance device.
An ink jet printer, which is one example of the recording apparatus, is usually equipped with a print head mounted on a carriage which travels back and forth in a main scanning direction, and a medium feeder for intermittently feeding a recording medium, such as print paper, in a sub-scanning direction in preset increments. The print head is actuated in the main scanning direction while the recording medium is being fed in the sub-scanning direction, and ink droplets are ejected toward the recording medium from the print head.
A mono-color ink jet printer is usually equipped with one print head. In contrast, a full-color ink jet printer is equipped with a black-ink print head for ejecting black ink, and a plurality of color-ink print heads for ejecting various colors of ink, such as yellow, cyan, and magenta.
A print head of an ink jet printer of such a construction has a pressure generation chamber and a nozzle orifice communicated therewith. Ink is stored in a pressure generation chamber and pressurized at a predetermined pressure, whereby ink droplets of controlled size are ejected from the nozzle orifice to the recording medium. Accordingly, when variations arise in the ink ejectability of the nozzle orifice of the print head, the quality of a recorded image is greatly affected. Hence, the ink ejectability must be maintained constant at all times.
The ink ejectability is changed by various phenomena, such as an increase in viscosity or solidification due to evaporation or drying of solvent in ink by way of the nozzle orifice, clogging due to solid material, adhesion of dust to the nozzles, and intrusion of air bubbles into ink. In order to prevent occurrence of such a change in characteristic, the ink jet printer is equipped with an ink ejectability maintenance device which eliminates the above-described phenomena causing variations to maintain the ink ejectability constant.
The ink ejectability maintenance device is equipped with a capping device, a suction pump, and a wiping device. The capping device is arranged so as to seal a nozzle formation face of a print head when no recording operation is performed, thereby isolating the nozzle orifice from the outside. Thus, the ink ejectability maintenance device has the function of inhibiting evaporation and drying of ink, thereby hindering an increase in viscosity and solidification of ink. Even when the nozzle formation face is sealed with the capping device, there cannot be completely prevented occurrence of clogging due to solid material in the nozzle orifice or intrusion of air bubbles into an ink flow channel. The ink jet printer is further equipped with a suction pump for the purpose of completely preventing occurrence of these problems.
The suction pump is configured so as to exert negative pressure on the nozzle orifice while the nozzle formation face is sealed with the capping device. The suction pump has the function of forcefully causing ink to be discharged from the nozzle orifice through suction, thereby eliminating solid material or air bubbles. Forceful discharge of ink to be performed by the suction pump is usually carried out when a recording operation is resumed after the ink jet printer has remained inoperative for a long time period or when the user has actuated a specifically-designed switch provided in a control panel with the understanding that deterioration of recorded image quality.
When ink is forcefully discharged by the suction pump, ink may splash across a nozzle formation face of the printer head, and in each nozzle orifice an ink meniscus may be disturbed. The nozzle formation face of the print head becomes susceptible to adhesion of extraneous matter with lapse of time. Hence, the print head is equipped with a wiping device for wiping the nozzle formation face, as required.
The wiping device has a wiping member whose base end is caught by a holder, and is constituted of an elastic plate such as rubber. An edge of the extremity of the wiping member is elastically pressed against a nozzle formation face, thereby effecting relative reciprocal movement so as to wipe the nozzle formation face. As a result, ink or extraneous matter adhering to the nozzle formation face is wiped, and ink meniscuses of respective nozzle orifices are made uniform. In short, the wiping device has the function of making the nozzle formation face stable.
The wiping device performs two types of wiping methods: a so-called horizontal wiping method and a so-called vertical wiping method. According to the horizontal wiping method, a wiper is set, and the print head is actuated in a printing direction: that is, a main scanning direction, thus wiping the nozzle formation face. According to the vertical wiping method, a print head is fixed, and a wiper is actuated in a paper feeding direction: that is, a sub-scanning direction, thus wiping the nozzle formation face. An appropriate wiping method is selected according to the type of ink: that is, dye, pigment, or reactive ink; the layout of a nozzle of a print head; or concentrated layout of a plurality of color nozzles on a print head with respect to either the main or sub-scanning direction.
When an attempt is made to apply any one of the wiping methods to one print head, there may arise a case where ink remains on either side of the print head, thereby soiling print paper. There has recently been proposed an ink jet printer equipped with one print head for ejecting only black ink and another print head on which nozzles for ejecting cyan ink, magenta ink, and yellow ink are arranged in the sub-scanning direction, wherein the two print heads are arranged side by side in the main scanning direction.
However, when such an ink jet printer employs ink which may coagulate when different colors of ink are mixed together, the two print heads cannot be wiped horizontally, because they are arranged side by side in the main scanning direction. Moreover, the cyan nozzles, the magenta nozzles, and the yellow nozzles are arranged in the sub-scanning direction, and hence the nozzles cannot be wiped vertically.
It is therefore an object of the present invention to provide an ink ejectability maintenance device having a wiping unit capable of completely wiping ink without involvement of mixing of different colors of ink, as well as a recorder having the ink ejectability maintenance device.
In order to achieve the above object, according to the present invention, there is provided an ink ejectability maintenance device for maintaining an ink ejectability of at least one recording head which ejects ink droplets to a recording medium, comprising:
a first wiper, which wipes a nozzle formation face of the recording head in a first direction; and
a second wiper, which wipes the nozzle formation face in a second direction perpendicular to the first direction.
Preferably, the first direction is a direction in which the recording head reciprocately moves, and the second direction is a direction in which the recording medium is fed.
Preferably, the first wiper and the second wiper are disposed on a single base member.
According to the above configurations, a recording apparatus having only one recording head can be subjected to two-way wiping action. Hence, ink can be wiped off completely without involvement of residues. In the case of a recording apparatus in which two recording heads are disposed side by side in the main scanning direction and a plurality of color nozzles are provided on one of the recording heads in the sub-scanning direction, even when there is used ink which would coagulate when colors of ink are mixed together, the respective recording heads can be wiped by changing the wiping direction. Hence, colors of ink can be wiped completely without mixing of ink.
Preferably, the first wiper extends in a direction which is slightly angled from the second direction, and the second wiper extends in a direction which is slightly angled from the first direction.
In this device, the two wipers can alternatively wipe only one print head of an ink-jet printer without interfering with each other. In addition, the load fluctuations acting on a carriage for moving the recording during the wiping operation can be decreased.
Preferably, the at least one recording head includes a first recording head for ejecting ink droplets of plural colors and a second recording head for ejecting ink droplets of a single color, which are arranged in the first direction. Here, the first wiper wipes a nozzle formation face of the first recording head, and the second wiper wipes a nozzle formation face of the second recording head.
In this device, even when there is used ink which would coagulate when colors of ink are mixed together, the respective recording heads can be wiped by changing the wiping direction. Hence, colors of ink can be wiped completely without mixing of ink.
Preferably, the ink ejectability maintenance device further comprises a driver unit which moves the single base member only in the second direction.
In this device, the number of parts can be reduced.
Here, it is preferable that the driver unit includes a pair of planetary gears which transmits a driving force thereof to the base member, and a single rotor which rotates either one of the planetary gears so that the driving force is transmitted by both of a forward rotation and a reverse rotation thereof.
Here, it is preferable that the driver unit includes a sun gear meshed with the respective planetary gears and a partially-chipped gear connected to the base member. The partially-chipped gear includes a cog portion which meshes either one of the planetary gears when the base member is moved, and a cogless portion which faces either one of the planetary gears after the base member is moved.
In this device, the position of the wiper can be readily initialized. Hence, there is obviated a necessity for effecting a sensing operation by setting a flag for detecting an initial position of the wipers on a cam for actuating the wiper. Hence, an attempt can be made to facilitate adjustment and assembly of the ink ejectability maintenance device and to curtail costs of the device. The wipers can be positioned in a predetermined location reliably by rotating the partially-chipped gear to a cogless portion through use of a planetary gear through a predetermined angle.
Here, it is preferable that the partially-chipped gear is a four-gears unit which respectively meshes the respective planetary gears and a wiper gear for driving the base member.
In this device, rotations of the respective planetary gears can be transmitted to the wiper gear without fail, and hence the positioning precision of the wipers can be improved.
Here, it is preferable that the wiper gear includes a lever for moving the base member in the second direction and a cam mechanism connected to the lever.
According to the present invention, there is also provided a recording apparatus comprising the above ink ejectability maintenance device.